Whoisology - Connected database of whois records and whois history
GRC Port Scan - GRC Internet Security Port Scanner. Tests for open ports on your external IP address.
WhoisThisDomain - Domain name lookup tool that allows you to get information about domain registration from WHOIS server.
My Public IP - My Public IP is a utility to let you know through which internet IP the world see you.
JSON WHOIS API - Parsed domain WHOIS data from any WHOIS server via RESTful API with metered pay as you pricing.
whatismyip.cc - External IP Address lookup tool with option to scan the external IP address.